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Discussion Starter #1
I have a problem with the front brakes during track days. Typically the brakes start squealing a little towards the end of a track day, which in itself is not a great problem but soon thereafter the brakes fade badly (with the brake lever coming all the way in to the throttle).

Being a new bike, I took it back to the dealer who simply bled the brakes, but the problem continued so he replaced the fluid with racing type (higher temperature) brake fluid. Apparently this was Honda's technical advice as they have had reports of 'boiling' of the fluid during track use.

Still not much better. Half way through a track day the brakes still fade, I usually fix it by 'banding' the brake lever with a cable tie and leaving it for 1/2 hr or so, which seems to get the bubbles out of the fluid and I can continue. Frankly I don't buy into the 'boiling' theory, as I'm no WSS rider and anyhow the higher temp brake fluid should have taken care fo that.


So the problem appears to be bubbles in the lines. Whilst no-one is sure where they're coming from, a number of possible solutions have been suggested;
- Replace with braided lines
- As above, but using 'dual' lines so there is no air trap as there is now.
- Replace master cyclinder with better quality. I don't know much about this, I don't mind doing it but I'm wondering what will happen to my ASV levers ...

And is this what is mean by a 'better' master cyclinder? (pic is of a Brembo radial pump for the 08CBR1000RR)



Has anyone else had any such issues? What have you done, and what do you suggest I do?
 

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So the problem appears to be bubbles in the lines. Whilst no-one is sure where they're coming from, a number of possible solutions have been suggested;
- Replace with braided lines
- As above, but using 'dual' lines so there is no air trap as there is now.
- Replace master cyclinder with better quality.
I don't know much about this, I don't mind doing it but I'm wondering what will happen to my ASV levers ...

Has anyone else had any such issues? What have you done, and what do you suggest I do?
If you are getting bubbles in the lines & no leaks then sounds like you are cooking the brakes.

1. So to keep the fluid temps working - change to a high spec 5.1 fluid.

2. Also change to a race brake pad for trackdays - this will be 'grippper (but not work well when cold) & will work better so you may use your brakes for less time.

3. Changing the lines to braided (I prefer the dual) is not a bad thing to do either.

The M/c I'd do last. See what happens with 1,2, & 3.
 

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Discussion Starter #3
Thank you Pete,

I have a higher temp brake fluid, I can find the bottle as I have kept it but the boiling point is much higher than the standard (dot4?) brake fluid. The dealer did this under warranty, but it costs about 3 times as much, it's about the best you can get or so he tells me. So that's that, unless you mean something else by 'higher spec'?

Re the pads, I also suggested that as I know racing pads are used in cars, but his advice was that it wouln't make any difference. Not saying that he's right mind you, just trying to understand it; would race pads stay cooler or not transfer head through as much?
Given that I have high temp fluid already, I can't help but feel that the problem lies elsewhere. I see no oil leaking out, but could air be getting sucked in? The oil is under positive pressure, so i don't see how ...
 

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Thank you Pete,

'higher spec'?

Re the pads, I also suggested that as I know racing pads are used in cars, but his advice was that it wouln't make any difference. Not saying that he's right mind you, just trying to understand it; would race pads stay cooler or not transfer head through as much?
Given that I have high temp fluid already, I can't help but feel that the problem lies elsewhere. I see no oil leaking out, but could air be getting sucked in? The oil is under positive pressure, so i don't see how ...
'higher spec'? - Not all 5.1 fluids are the same

If the pads are 'grippier you will:
1. stop quicker
2. brake for less time = less heat transfer...

On another track to check for fluid boiling (& I am sure you have this) you can put some 'Thermal paint' on your calipers or temp strips. This will give you an idea of the temps you're getting to. check this:
http://www.apracing.com/info/info.asp?section=Brake+Temperatures_44
 

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Sounds like you have a leak. I know someone said you don't, but you might have one. Here are some quick things you can do before you go out and sell the ship on the brakes:

1) Get braided lines. As fluid heats up, the rubber lines can expand effectively reducing your braking capacity. SS lines will keep all that in check. They don't expand as readily as the rubber lines.

2) Pick up some new brake pads. I'm a Vesrah man myself. RJLs are a good place to start. But any capable pad is fine.

3) Replace your brake fluid (you will anyways when you switch the lines) to a good, reputable brand. I use Motul RBF. Works fantastic. I'm super slow, so I need to catch up to people on the brakes. And I wouldn't have anything less in my system. It's DOT4.

Do all those things first and see if your braking performance gets better. Those are the simple "must do"'s of braking upgrades.

After all is said and done, if you're still experiencing fade, then I would highly consider that you have a leak somewhere in your system. The first place I would check is the Master Cylinder. If you can't find a good OEM replacement for cheap, and want to step up, I HIGHLY recommend a Brembo MC.

If I had the $$$, I would pick up a Brembo MC in a heart beat. I swapped bikes with my buddy one time and he has basically the same set up as my bike, except he has a Brembo MC. WOW! THE most linear, progressive, smooooooooooth braking application I have EVER experienced. It was like "buttah". Highly recommend a radial MC in the Brembo variant. Or, really, any high end MC from the likes as Nissin or others.
 

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Discussion Starter #7 (Edited)
Thanks you for the advice, I will replace the lines (twin lines with no air trap) and see what that does. I have been told that even if there's a leak somewhere, the twin lines could let the bubbles work their way up, whereas now there is that air trap on the line 'loop' above the fender.

Sooperman, what will happen to the ASV levers if I fit a new master cylinder? Looking at the pic of the Brembo one on my original post, it looks like it needs a different lever?

PS. The brake fluid I have in it is MOTUL RBF600 Racing Brake Fluid. Dry boiling point is 594F, whereas Motul dot 4 is 473F.

PPS. Another question; are any braided lines better than others? I was going to get these ones: http://www.motomummy.com/store/product.php?productid=16206&cat=292&page=1
 

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If your brakes work normally after 'banding the lever for 1/2 hour' then how is it possible you have a leak?
Even if you have a'small amount of air' trapped then that would be reflected in the lever at all times.

Racing your bike is hard on the braking system
Please note: Overheated brake fluid can (and will) boil in the caliper. Boiling produces gas bubbles within any boiling fluid. Gas is compressible so boiling brake fluid leads to a “soft” brake pedal with long travel. In extreme cases overheated brake fluid necessitates “pumping the brake pedal” in order to get a pedal at all. This will explain why your brakes - come back to life after banding the lever.

On the lines they look fine & I'd get rid of the rubber ones on the track anyway.

Hel, Goodridge, Galfer all make excellent lines as well.

Is this a track only bike? - running street tyres?
 

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Discussion Starter #9 (Edited)
I use it for the track and the road ... although to be honest it's mostly track. I have it on Pilot Powers 2CT.

Somehow the brake fluid must be 'boiling' - or let's say there's air entering the system, and I suspect it has something to do with the 'squealing' which usually starts just before the fading, but the mechanic told me that they cannot be related (I don't believe it, the pattern is there). Also it's a normal track day, and given the higher temp fluid I find it hard to understand how the fluid could be boiling. Is there another way for the bubbles to enter the system?
 

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get SS lines and dual sintered pads. I had your problem on my first trackday. within a week i was running spiegler lines, vesrah RJL's and motul 5.1 fluid. done 5 trackdays since then and not one problem at all. my braking is progressive, consistent and strong. i highly recommend some SS lines, good pads and good fluid. i don't think anything else is necessary. don't worry about the lever or the master cylinder- that's not the problem. if you have to pick only one- i'd say, at least get SS lines if you do nothing else. that alone should pretty much stomp the problem out since it's most likely rooted in the flex that the $hitty rubber stock lines have.
 

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Discussion Starter #11
Thanks Dr, sounds like good advice. Just one thing ... what are 'dual sintered pads'?

Also - the 'SS lines', do you mean 'braided lines' like the ones that I posted the motomummy link for (post # 7)?

Sorry if my questions are a little basic ....
 

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Went through same problems.

The fix is just what has already been suggested.

stainless lines,
Motul RBF600
Vesrah RJL

I've never used the Brembro. I'm sure its as good as everyone says. MC's are about $350. I'm quite sure if you do the pads,lines, and fluid you will be happy.
 
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